Generally, ink jet printer-printed materials, a thermo-transfer materials or information-recording materials having an image carrier layer composed of a hydrophilic polymer such as a silver halide light-sensitive material are poor in moisture resistance. They easily spot at the slightest touch of drops of moisture. In addition, fingerprints show readily and sticking is also a problem.
Due to the above, heretofore, a protective layer was often provided on image recording surfaces. For preparing such a protective layer, technologies of coating a radiographic hardening resin and hardening it with radiographic radiation are disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter, referred to as Japanese Patent O.P.I. Publication) Nos. 57023/1978, 201248/1986 and 21150/1987. However, the above-mentioned technologies have the following shortcomings: namely, the above-mentioned layers exhibited insufficient adhesion with the image carrier layer. There were also problems in terms of toxicity to exposed skin. It was difficult to counter these shortcoming. An apparatus to irradiate with radiographic rays was necessary. In addition, there were many other shortcomings including cost, safety and complexity.
In addition, technologies to laminate an information-recording material having an image carrier layer are disc losed in Japanese Patent O.P.I. Publication Nos. 62360/1987 and 259570/1988. However, these methods are so expensive that they are not employed in ordinary inexpensive printing material and printing photography, except for special applications.
In addition, technologies to form a protective covering layer of the information-recording material by means of resin latex are disclosed in Japanese Patent O.P.I. Publication Nos. 247370/1987 and 110169/1994. Further, a technology to obtain the protective covering layer by means of an ionic polyester is disclosed in 212640/1991. These technologies improved water resisting property only slightly. In addition, scratch resistance deteriorated. Therefore, they were hard to be accepted by the market.
In addition, it is commonly known that polyurethane is used for photographic recording materials and that aforesaid polyurethane is used in conjunction with gelatin, a hydrophilic colloid. For example, Japanese Patent Publication No. 36365/1975, Japanese Patent O.P.I. Publication Nos. 67841/1981, 145556/1986 and 56651/1987, British Patent Nos. 1345741 and 2063500, European Patent No. 185248, West German Patent No. 1472746 and U.S. Pat. No. 3,607,289 disclose technologies to utilize ionic polyurethane for improvement in terms of fragility of the gelatin layer and for improved sensitivity. However, most of the anionic polyurethanes disclosed in the above-mentioned patents have structures in which sulfonic acid or its salt or phosphoric acid or its salt is introduced to a terminal group. In addition, with regard to its form, aforesaid polyurethane is mixed with gelatin, which is a hydrophilic colloid, to form a binder. Therefore, the above-mentioned polyurethanes are not used in protective covering layers.